Short-range wireless communication techniques have been used in various fields to transmit and receive data in a contactless manner. Radio frequency identification (RFID) is a widespread, typical short-range wireless communication technique. A common RFID system includes an RF tag attached to a target object (hereafter, a workpiece) or an object such as a pallet or a container supporting or containing the target object, an interrogation device (hereafter, a reader/writer) that transmits and receives data to and from the RF tag, and a host device that controls the reader/writer.
At production sites such as factories and at sites for physical distribution management, accurately transmitting and receiving data is important to improve production efficiency and management efficiency. Interrogation with RFID tags is desired to avoid reading unintended RFID tags (hereafter, over-reading) and avoid failing to read intended RFID tags (hereafter, under-reading). Over-reading occurs when an unintended RFID tag is determined as a target for a read/write process, whereas under-reading occurs when an intended RFID tag cannot be determined as a target for a read/write process.
To prevent over-reading and under-reading, a technique for identifying a target RFID tag is described in, for example, Japanese Unexamined Patent Application Publication No. 2013-037663 (Patent Literature 1). Patent Literature 1 describes a method for identifying a target RFID tag based on the reading count, changes in the strength of a received signal, and changes in the phase of the received signal.